Many ways of recovering some of the heat in the grey waste water of a shower to preheat the incoming cold water have been attempted in the past. The prior art of Hunter's Shower Bath Economizer (U.S. Pat. No. 4,372,372) uses a chamber below the drain with a helical coil within forming a type of coil-in-shell heat exchanger. Nobile, in his heat recovery device of U.S. Pat. No. 5,791,401, uses a coil of tubing containing the incoming cold water wrapped around a formed section of the drain pipe to recover heat from the waste water. Vasile et al. in his U.S. Pat. No. 4,619,311 uses a contraflow heat exchanger formed around the straight drain pipe to the sewer to recover some heat. Sheffield, in his U.S. Pat. No. 4,821,793, uses an above the floor tub and shower floor heat exchanger for the same heat recovery function.
The prior art of Cardone's U.S. Pat. No. 4,304,292 for a shower waste heat recovery system is described in detail in FIGS. 1-6 provided below. While it is a workable system for recovery of heat from the grey waste water, it did have a shortcoming such that it was not compatible with some plumbing codes regarding removability of clogs in the drain.
In the prior art of Cardone '292, with the significant shortcoming subsequently noted above, it already is known that use is made of discharging water from a household shower, either of the tub-type 30 or stall-type 32, to effectuate significant energy conservation, wherein as is typically the case, the household has a boiler 34 of the type which includes a storage tank 36 which tank, depending upon boiler-heated water available for use for such purposes as showering at locations 30, 32.
The prior art will be understood for the set-up for the showers 30 or 32 to include a tub drain conduit 40 or a stall shower drain 42, wherein the drain channels the discharging water through a trap of U-shaped design designated 44, on its way to a sewer connection 46.
It is known that the water discharging through the U-shaped conduit 44 is, in most cases, tepid, being a mixture of boiler-heated warm water and a cold water input to the showers, 30, 32.
In the above respect, it has been noted that the discharging water that normally drains is approximately 100° Fahrenheit at the time encountering the U-shaped conduit 44. This otherwise wasted 100° Fahrenheit water is effectively passed in heat exchange relation to the cold water input, which in the community of Wantagh, N.Y., is typically supplied at 50° Fahrenheit. The heat exchange has been found in practice to provide a lukewarm water source at approximately 65° to 75° Fahrenheit for delivery to the faucet connection 58, 60 of the showers 30, 32. This increase in approximately 15° to 25° Fahrenheit significantly diminishes the amount of boiler-heated water that is required to be delivered to the showers 30, 32. While the beneficial results depend on different operating conditions and thus cannot be defined with precision, in practice use of the invention for 28 successive showers at a selected tepid temperature of 110° Fahrenheit for the premixed water and during a selected duration time for showering of 10 minutes which consumed approximately 15 gallons of the prior art set-up of FIG. 1.
Cardone's U.S. Pat. 4,304,292 for heat conservation, unfortunately with the shortcoming noted above, is nevertheless commendably practiced as best illustrated in FIGS. 5 and 6, which correspond to FIGS. 8 and 9 of Cardone '292, as well as what is shown in the crossectional detail view of FIG. 10 of Cardone '292, in which a floor of shower 30′ includes a base 100 in the upper face or surface 102 of which there is embodied, in any appropriate manner, a spiral trough, generally designated 104 in FIG. 6 and the individual helical turns of which are designated individually and collectively 106. By slight increases in depth of the individual helical turns 106 the trough 104 is pitched to drain towards central opening 108 of base 100 of FIG. 10 of Cardone '292,, in which opening there is an appropriate drain fitting (not shown) which mounts a depending conduit (not shown) which will be understood to discharge into a sewer or the like. In accordance with the prior art, a pipe 114 suitable for flowing water to the shower (not shown) and itself in a helical configuration as illustrated, is deposited in the correspondingly helically configurated trough 104. That is, and as is perhaps best illustrated in FIG. 6, the individual helical turns of the spiral pipe 114, designated individually and collectively 116 are each located in a cooperating one of the helical turns 106 of the spiral trough 104. Connected at the center, as at 118 to the spiral pipe 114, is the shower cold water inlet pipe or conduit 122, as shown in Prior Art FIG. 6 herein, and in FIG. 9 of Cardone '292. The cold water outlet connection from the spiral pipe 114, designated 120, extends from the outermost helical turn and is connected to the shower faucet cold water conduit 56′. As a result, the cold water input to the shower 30′ is delivered through the helical heat exchanger 114 prior to delivery through the shower head (not shown). More particularly, cold water from a suitable source initially flows through the inlet pipe 120, then successively through each of the helical turns 116 to the helical pipe 114, and then finally through the outlet pipe 120 into the faucet pipe 56′ where, upon opening of the valve (not shown), the water is discharged through the shower nozzle (not shown).
However, the prior art of Cardone '292 does not reveal a shower heat recovery system using a high efficiency flat plate heat exchanger with specific features for drain clog removal.